"Not everyone will like you and that's okay." 21 life lessons everyone should learn by 21.

This week, I turned 21. I can't tell you how relieved I was to finally hit that milestone, which I had so desperately waited for.

You see, in your teens, you're still just a teenager. Then at 20, you're still a little too close to being a teen to garner the same respect as a typical adult. 

But in my eyes, 21 was the marker of adulthood, and I was immediately filled with wisdom to impart on anyone in my vicinity. 

Watch: The horoscopes and break-ups. Post continues below.

"Growth begins where your comfort zone ends!" I'd yell at school kids as I drove past. "The future is long and bright!" 

I know, I know, I can hear you rolling your eyes already. "You're SO young! You have such a long life ahead of you! How much can you really know at 21?"

Not much, actually. You're probably right.

But indulge me for a minute, because I believe there are some valuable things you learn in your teens and early 20s that (I'd hope) build the foundations for a prosperous life ahead. 

And it'd be rude not to share my pre-empted wisdom with you, right now.

1. A haircut can fix most things.

Haircuts are deeply underrated. Let me explain. 

Going through a breakup? Starting a new job? Just feeling generally sh*tty? Fight me on this all you like, but spending hundreds of dollars on a hair transformation will have you ready to face the world immediately.

Sure, an emotional transformation would be great, but that could take years in therapy.

When you're feeling a little flat, book yourself into the hairdressers and give them creative range to style you as they please.

Take my pre-and-post hair transformation pics:

I mean, they speak for themselves. Image: Supplied.

Disclaimer: A bad haircut can ruin many things too. Please proceed with caution and employ trusted hair professionals only. 

2. Nothing worth staying for happens after 3am.

Growing up, my mum always told me that nothing good happens after 12am. 

I disagree. I don't think there's any expiry on having a good time. (But then again, maybe that's a lesson for me to learn in my 30s. ¯\_(ツ)_/¯)

I love going out and having a boogie, but the saying should really be: whatever happens after 3am probably isn't worth the weekend-long recovery.

Yeah, kick-ons at a friend's house might sound like a good idea when you're seven vodka sodas deep, but the very second it hits 3am, I can guarantee you'll be regretting your decision the next day. 

Pull yourself away. ASAP.

3. Romantic relationships will come and go. Invest in your friendships.

Ah, this one took me a good while to learn. 

But please, take it from me. You probably won't be with your high school boyfriend forever, and you're wasting precious friendship bonding time by spending every waking minute with them.

It's such a blessing to have a range of people you can count on (and that can count on you!)

Spend time with your friends, family, romantic partners, coworkers, pets, and that gym buddy you always seem to run into on Tuesday, because varied relationships are the spice of life and no one person should fill all of your tank.

4. Not everyone will like you and that's okay.

About a year ago, I was sitting across from my psychologist discussing my incessant need for people to like me when we had a bit of an epiphany.

"I've realised that I alter myself a little bit every time I meet someone new to be the person I think they'd like best," I told him.

"Why do you care if they like you or not if you're not even being yourself?" he responded. 

He was right (he often is). I wasn't letting people like or dislike me based on my own merit. I was pre-empting their rejection by presenting as the person they might want me to be. 

But I'm not a mind reader, so not only did I not get to enjoy being myself, but it didn't even work a lot of the time, and it was messing with my sense of self and identity.

Of course, I argued that it would be too hard to know that someone doesn't like me for the person I really am.

"But at least you'd know," he told me.

And so I went forth accepting that I'm not everyone's cup of tea and it was a whole lot less exhausting when I wasn't analysing and changing myself for those around me.

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5. People don't think about you the same way you do.

Speak up. Do the thing. People are not sitting around, waiting for you to f*ck up. In fact, they'd probably love to hear what you really think.

We're all far too distracted thinking about ourselves to worry about others, anyway.

6. The expensive tuna is worth it.

I've tried other brands. 

Sirena Tuna just hits different and if it means spending a few more dollars on my weekly shop, so be it.

7. Be kinder.

Kindness is good for the soul. None more than your own.

When I'm feeling irritable and impatient, or when someone cuts me off in traffic and my default response is to scream at them for being so careless, more and more recently I've stopped myself in my tracks to see how getting angry benefits no one. Me included.

I don't want to have someone leave an interaction with me feeling angry, or frustrated, or upset the same way someone screaming at me might.

So always treat people with kindness, even when they don't deserve it. Aside from potentially making someone's day, you'll also be a hell of a lot happier yourself.

Side note: Listen to Mamamia's podcast The Undone, a a show about navigating the "adult" world without a GPS, friendship, love, sex, personal politics, and... air fryers. Post continues below.

8. Renting is an investment when it means you don't have to live at home.

Am I tens of thousands of dollars poorer a year because I don't live at home anymore? Yes.

Would I do it again? Every bloody time. 

I love my family. Don't get me wrong. But I will bask in my plant-filled, cheaply furnished share-apartment with so much gratitude to have all the bill-paying independence I so desperately craved as a teenager.

9. Being cool is a capitalist scam that limits creativity.

Further to my point that not everyone will like you, most cool and trendy things exist to make super rich people richer, and to dampen individuality. 

Give it up. Be yourself as you so please!

10. Growth begins where your comfort zone ends.

I used to despise leaving my comfort zone. I would die happy not trying new foods and never leaving my 5km bubble. 

Then I realised how much good sh*t happens when you're not doing the same thing every day, and since then, I started nudging myself to try new things wherever possible.

You learn a lot about yourself this way, and as uncomfortable as it might be, I think you'll find it's worth it.

11. Don't underestimate the power of a good playlist

At 21, I think I've finally managed to curate playlists that will suit any and every mood I could possibly feel. I mean, I literally have one called: my heart was broken by a Gemini, because we've all been there right?

Once you discover the power of music to cushion your most drastic moods, getting through the best and worst times in life will be that little bit easier.

Relatedly: 

12. A bluetooth speaker will always be an important investment.

Maybe not everyone needs a portable bluetooth speaker, but when you can't afford fancy surround sound speakers at your rental apartment and you drive a 2004 Toyota Corolla with no bluetooth or aux capabilities, a bluetooth speaker is not simply a bluetooth speaker: it's a lifeline.

13. You probably need a nap.

Enough said.

14. Listen more.

God, I used to looooooove talking about myself. 

Well, I still do, but at least now I'm self aware. 

If you're anything like me, you can never listen enough. Because everyone wants to be heard, but also because it's such a pleasure to really understand someone else.

It takes practice. Buy yourself a drink and just keep sipping on it. But just stop talking for a moment.

15. You'll make the same mistake at least three times.

Hi, I'm Emma, and I'm a serial parking fine offender.

I know what I'm doing when I park in a two-hour spot knowing I'll be closer to three. Or when I don't pay for a ticket because parking in Sydney is outrageous, and the council doesn't really need my money.

But it backfires every single time and I always beat myself up about it. 

"You know better than this, Emma. This is the second time this month, just buy the bloody parking ticket!"

Then I discovered something. You'll probably make the same mistake three times. Maybe for you it's parking fines, or maybe it's going for the artsy boy who uses his alty vibe as an excuse to gaslight you. 

But every time you make that same mistake, you learn a little more not to do it again.

And hopefully by round four you've got it in the bag.

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16. If they show you they don't want you, believe them.

I've spent far too many hours waiting on a response, arranging plans, and chasing after a guy who is happy for some company, but isn't willing to lift a finger for any form of a relationship.

They're not going to change, and even if they did, you deserve someone who wants you the first time. 

I know it's hard. Now leave it.

17. Find a good book.

Reading is heavenly — with the right material. Rediscover books and let yourself escape from the chaos into a good trashy novel. It feels like free therapy. 

Side note: I've got a list of my top reccos to get you reading again right here. 

18. The Uber Eats usually isn't worth it.

Has anyone else noticed the service and delivery fees nowadays? Delivery food is expensive and you probably have something in the cupboard.

19. Buy the jeans that fit. 

Not the ones you want to fit.

20. Find your quick and easy dinner and life gets easier.

Mine? Spaghetti with butter and parmesan cheese. If I have some ham, I might throw that in there too. 

If you have the ingredients for a quick meal at home when you need them, you might also avoid that Uber Eats fee that I hate so much. 

21. You haven't got it worked out yet, and that's GOOD.

I'm pretty hard on myself.

I want to have all the answers, but I just don't. And once I accepted that, I also accepted that learning things, growing, and riding the ~wave of life~ is fun as it is. 

Sometimes it's okay to be the passenger of your journey instead of sitting at the captain's seat 24/7, right?

For more 20-something antics from Emma, you can find her on Instagram: @emma.gillman.

Feature Image: Supplied.